/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_conv_partial_fast_q31.c
*
* Description:	Fast Q31 Partial convolution.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.11 2011/10/18
*    Bug Fix in conv, correlation, partial convolution.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup PartialConv
 * @{
 */

/**
 * @brief Partial convolution of Q31 sequences (fast version) for Cortex-M3 and Cortex-M4.
 * @param[in]       *pSrcA points to the first input sequence.
 * @param[in]       srcALen length of the first input sequence.
 * @param[in]       *pSrcB points to the second input sequence.
 * @param[in]       srcBLen length of the second input sequence.
 * @param[out]      *pDst points to the location where the output result is written.
 * @param[in]       firstIndex is the first output sample to start with.
 * @param[in]       numPoints is the number of output points to be computed.
 * @return Returns either ARM_MATH_SUCCESS if the function completed correctly or ARM_MATH_ARGUMENT_ERROR if the requested subset is not in the range [0 srcALen+srcBLen-2].
 *
 * \par
 * See <code>arm_conv_partial_q31()</code> for a slower implementation of this function which uses a 64-bit accumulator to provide higher precision.
 */

arm_status arm_conv_partial_fast_q31(
    q31_t* pSrcA,
    uint32_t srcALen,
    q31_t* pSrcB,
    uint32_t srcBLen,
    q31_t* pDst,
    uint32_t firstIndex,
    uint32_t numPoints)
{
	q31_t* pIn1;                                   /* inputA pointer               */
	q31_t* pIn2;                                   /* inputB pointer               */
	q31_t* pOut = pDst;                            /* output pointer               */
	q31_t* px;                                     /* Intermediate inputA pointer  */
	q31_t* py;                                     /* Intermediate inputB pointer  */
	q31_t* pSrc1, *pSrc2;                          /* Intermediate pointers        */
	q31_t sum, acc0, acc1, acc2, acc3;             /* Accumulators                  */
	q31_t x0, x1, x2, x3, c0;
	uint32_t j, k, count, check, blkCnt;
	int32_t blockSize1, blockSize2, blockSize3;    /* loop counters                 */
	arm_status status;                             /* status of Partial convolution */


	/* Check for range of output samples to be calculated */
	if((firstIndex + numPoints) > ((srcALen + (srcBLen - 1u)))) {
		/* Set status as ARM_MATH_ARGUMENT_ERROR */
		status = ARM_MATH_ARGUMENT_ERROR;
	} else {

		/* The algorithm implementation is based on the lengths of the inputs. */
		/* srcB is always made to slide across srcA. */
		/* So srcBLen is always considered as shorter or equal to srcALen */
		if(srcALen >= srcBLen) {
			/* Initialization of inputA pointer */
			pIn1 = pSrcA;

			/* Initialization of inputB pointer */
			pIn2 = pSrcB;
		} else {
			/* Initialization of inputA pointer */
			pIn1 = pSrcB;

			/* Initialization of inputB pointer */
			pIn2 = pSrcA;

			/* srcBLen is always considered as shorter or equal to srcALen */
			j = srcBLen;
			srcBLen = srcALen;
			srcALen = j;
		}

		/* Conditions to check which loopCounter holds
		 * the first and last indices of the output samples to be calculated. */
		check = firstIndex + numPoints;
		blockSize3 = ((int32_t) check - (int32_t) srcALen);
		blockSize3 = (blockSize3 > 0) ? blockSize3 : 0;
		blockSize1 = (((int32_t) srcBLen - 1) - (int32_t) firstIndex);
		blockSize1 = (blockSize1 > 0) ? ((check > (srcBLen - 1u)) ? blockSize1 :
		                                 (int32_t) numPoints) : 0;
		blockSize2 = (int32_t) check - ((blockSize3 + blockSize1) +
		                                (int32_t) firstIndex);
		blockSize2 = (blockSize2 > 0) ? blockSize2 : 0;

		/* conv(x,y) at n = x[n] * y[0] + x[n-1] * y[1] + x[n-2] * y[2] + ...+ x[n-N+1] * y[N -1] */
		/* The function is internally
		 * divided into three stages according to the number of multiplications that has to be
		 * taken place between inputA samples and inputB samples. In the first stage of the
		 * algorithm, the multiplications increase by one for every iteration.
		 * In the second stage of the algorithm, srcBLen number of multiplications are done.
		 * In the third stage of the algorithm, the multiplications decrease by one
		 * for every iteration. */

		/* Set the output pointer to point to the firstIndex
		 * of the output sample to be calculated. */
		pOut = pDst + firstIndex;

		/* --------------------------
		 * Initializations of stage1
		 * -------------------------*/

		/* sum = x[0] * y[0]
		 * sum = x[0] * y[1] + x[1] * y[0]
		 * ....
		 * sum = x[0] * y[srcBlen - 1] + x[1] * y[srcBlen - 2] +...+ x[srcBLen - 1] * y[0]
		 */

		/* In this stage the MAC operations are increased by 1 for every iteration.
		   The count variable holds the number of MAC operations performed.
		   Since the partial convolution starts from firstIndex
		   Number of Macs to be performed is firstIndex + 1 */
		count = 1u + firstIndex;

		/* Working pointer of inputA */
		px = pIn1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + firstIndex;
		py = pSrc2;

		/* ------------------------
		 * Stage1 process
		 * ----------------------*/

		/* The first loop starts here */
		while(blockSize1 > 0) {
			/* Accumulator is made zero for every iteration */
			sum = 0;

			/* Apply loop unrolling and compute 4 MACs simultaneously. */
			k = count >> 2u;

			/* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
			 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
			while(k > 0u) {
				/* x[0] * y[srcBLen - 1] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* x[1] * y[srcBLen - 2] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* x[2] * y[srcBLen - 3] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* x[3] * y[srcBLen - 4] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* Decrement the loop counter */
				k--;
			}

			/* If the count is not a multiple of 4, compute any remaining MACs here.
			 ** No loop unrolling is used. */
			k = count % 0x4u;

			while(k > 0u) {
				/* Perform the multiply-accumulates */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* Decrement the loop counter */
				k--;
			}

			/* Store the result in the accumulator in the destination buffer. */
			*pOut++ = sum << 1;

			/* Update the inputA and inputB pointers for next MAC calculation */
			py = ++pSrc2;
			px = pIn1;

			/* Increment the MAC count */
			count++;

			/* Decrement the loop counter */
			blockSize1--;
		}

		/* --------------------------
		 * Initializations of stage2
		 * ------------------------*/

		/* sum = x[0] * y[srcBLen-1] + x[1] * y[srcBLen-2] +...+ x[srcBLen-1] * y[0]
		 * sum = x[1] * y[srcBLen-1] + x[2] * y[srcBLen-2] +...+ x[srcBLen] * y[0]
		 * ....
		 * sum = x[srcALen-srcBLen-2] * y[srcBLen-1] + x[srcALen] * y[srcBLen-2] +...+ x[srcALen-1] * y[0]
		 */

		/* Working pointer of inputA */
		px = pIn1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + (srcBLen - 1u);
		py = pSrc2;

		/* count is index by which the pointer pIn1 to be incremented */
		count = 0u;

		/* -------------------
		 * Stage2 process
		 * ------------------*/

		/* Stage2 depends on srcBLen as in this stage srcBLen number of MACS are performed.
		 * So, to loop unroll over blockSize2,
		 * srcBLen should be greater than or equal to 4 */
		if(srcBLen >= 4u) {
			/* Loop unroll over blockSize2 */
			blkCnt = ((uint32_t) blockSize2 >> 2u);

			while(blkCnt > 0u) {
				/* Set all accumulators to zero */
				acc0 = 0;
				acc1 = 0;
				acc2 = 0;
				acc3 = 0;

				/* read x[0], x[1], x[2] samples */
				x0 = *(px++);
				x1 = *(px++);
				x2 = *(px++);

				/* Apply loop unrolling and compute 4 MACs simultaneously. */
				k = srcBLen >> 2u;

				/* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
				 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
				do {
					/* Read y[srcBLen - 1] sample */
					c0 = *(py--);

					/* Read x[3] sample */
					x3 = *(px++);

					/* Perform the multiply-accumulate */
					/* acc0 +=  x[0] * y[srcBLen - 1] */
					acc0 = (q31_t)((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);

					/* acc1 +=  x[1] * y[srcBLen - 1] */
					acc1 = (q31_t)((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);

					/* acc2 +=  x[2] * y[srcBLen - 1] */
					acc2 = (q31_t)((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);

					/* acc3 +=  x[3] * y[srcBLen - 1] */
					acc3 = (q31_t)((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);

					/* Read y[srcBLen - 2] sample */
					c0 = *(py--);

					/* Read x[4] sample */
					x0 = *(px++);

					/* Perform the multiply-accumulate */
					/* acc0 +=  x[1] * y[srcBLen - 2] */
					acc0 = (q31_t)((((q63_t) acc0 << 32) + ((q63_t) x1 * c0)) >> 32);
					/* acc1 +=  x[2] * y[srcBLen - 2] */
					acc1 = (q31_t)((((q63_t) acc1 << 32) + ((q63_t) x2 * c0)) >> 32);
					/* acc2 +=  x[3] * y[srcBLen - 2] */
					acc2 = (q31_t)((((q63_t) acc2 << 32) + ((q63_t) x3 * c0)) >> 32);
					/* acc3 +=  x[4] * y[srcBLen - 2] */
					acc3 = (q31_t)((((q63_t) acc3 << 32) + ((q63_t) x0 * c0)) >> 32);

					/* Read y[srcBLen - 3] sample */
					c0 = *(py--);

					/* Read x[5] sample */
					x1 = *(px++);

					/* Perform the multiply-accumulates */
					/* acc0 +=  x[2] * y[srcBLen - 3] */
					acc0 = (q31_t)((((q63_t) acc0 << 32) + ((q63_t) x2 * c0)) >> 32);
					/* acc1 +=  x[3] * y[srcBLen - 2] */
					acc1 = (q31_t)((((q63_t) acc1 << 32) + ((q63_t) x3 * c0)) >> 32);
					/* acc2 +=  x[4] * y[srcBLen - 2] */
					acc2 = (q31_t)((((q63_t) acc2 << 32) + ((q63_t) x0 * c0)) >> 32);
					/* acc3 +=  x[5] * y[srcBLen - 2] */
					acc3 = (q31_t)((((q63_t) acc3 << 32) + ((q63_t) x1 * c0)) >> 32);

					/* Read y[srcBLen - 4] sample */
					c0 = *(py--);

					/* Read x[6] sample */
					x2 = *(px++);

					/* Perform the multiply-accumulates */
					/* acc0 +=  x[3] * y[srcBLen - 4] */
					acc0 = (q31_t)((((q63_t) acc0 << 32) + ((q63_t) x3 * c0)) >> 32);
					/* acc1 +=  x[4] * y[srcBLen - 4] */
					acc1 = (q31_t)((((q63_t) acc1 << 32) + ((q63_t) x0 * c0)) >> 32);
					/* acc2 +=  x[5] * y[srcBLen - 4] */
					acc2 = (q31_t)((((q63_t) acc2 << 32) + ((q63_t) x1 * c0)) >> 32);
					/* acc3 +=  x[6] * y[srcBLen - 4] */
					acc3 = (q31_t)((((q63_t) acc3 << 32) + ((q63_t) x2 * c0)) >> 32);


				} while(--k);

				/* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
				 ** No loop unrolling is used. */
				k = srcBLen % 0x4u;

				while(k > 0u) {
					/* Read y[srcBLen - 5] sample */
					c0 = *(py--);

					/* Read x[7] sample */
					x3 = *(px++);

					/* Perform the multiply-accumulates */
					/* acc0 +=  x[4] * y[srcBLen - 5] */
					acc0 = (q31_t)((((q63_t) acc0 << 32) + ((q63_t) x0 * c0)) >> 32);
					/* acc1 +=  x[5] * y[srcBLen - 5] */
					acc1 = (q31_t)((((q63_t) acc1 << 32) + ((q63_t) x1 * c0)) >> 32);
					/* acc2 +=  x[6] * y[srcBLen - 5] */
					acc2 = (q31_t)((((q63_t) acc2 << 32) + ((q63_t) x2 * c0)) >> 32);
					/* acc3 +=  x[7] * y[srcBLen - 5] */
					acc3 = (q31_t)((((q63_t) acc3 << 32) + ((q63_t) x3 * c0)) >> 32);

					/* Reuse the present samples for the next MAC */
					x0 = x1;
					x1 = x2;
					x2 = x3;

					/* Decrement the loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = (q31_t)(acc0 << 1);
				*pOut++ = (q31_t)(acc1 << 1);
				*pOut++ = (q31_t)(acc2 << 1);
				*pOut++ = (q31_t)(acc3 << 1);

				/* Increment the pointer pIn1 index, count by 4 */
				count += 4u;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pIn1 + count;
				py = pSrc2;

				/* Decrement the loop counter */
				blkCnt--;
			}

			/* If the blockSize2 is not a multiple of 4, compute any remaining output samples here.
			 ** No loop unrolling is used. */
			blkCnt = (uint32_t) blockSize2 % 0x4u;

			while(blkCnt > 0u) {
				/* Accumulator is made zero for every iteration */
				sum = 0;

				/* Apply loop unrolling and compute 4 MACs simultaneously. */
				k = srcBLen >> 2u;

				/* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
				 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
				while(k > 0u) {
					/* Perform the multiply-accumulates */
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);

					/* Decrement the loop counter */
					k--;
				}

				/* If the srcBLen is not a multiple of 4, compute any remaining MACs here.
				 ** No loop unrolling is used. */
				k = srcBLen % 0x4u;

				while(k > 0u) {
					/* Perform the multiply-accumulate */
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);

					/* Decrement the loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = sum << 1;

				/* Increment the MAC count */
				count++;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pIn1 + count;
				py = pSrc2;

				/* Decrement the loop counter */
				blkCnt--;
			}
		} else {
			/* If the srcBLen is not a multiple of 4,
			 * the blockSize2 loop cannot be unrolled by 4 */
			blkCnt = (uint32_t) blockSize2;

			while(blkCnt > 0u) {
				/* Accumulator is made zero for every iteration */
				sum = 0;

				/* srcBLen number of MACS should be performed */
				k = srcBLen;

				while(k > 0u) {
					/* Perform the multiply-accumulate */
					sum = (q31_t)((((q63_t) sum << 32) +
					               ((q63_t) * px++ * (*py--))) >> 32);

					/* Decrement the loop counter */
					k--;
				}

				/* Store the result in the accumulator in the destination buffer. */
				*pOut++ = sum << 1;

				/* Increment the MAC count */
				count++;

				/* Update the inputA and inputB pointers for next MAC calculation */
				px = pIn1 + count;
				py = pSrc2;

				/* Decrement the loop counter */
				blkCnt--;
			}
		}


		/* --------------------------
		 * Initializations of stage3
		 * -------------------------*/

		/* sum += x[srcALen-srcBLen+1] * y[srcBLen-1] + x[srcALen-srcBLen+2] * y[srcBLen-2] +...+ x[srcALen-1] * y[1]
		 * sum += x[srcALen-srcBLen+2] * y[srcBLen-1] + x[srcALen-srcBLen+3] * y[srcBLen-2] +...+ x[srcALen-1] * y[2]
		 * ....
		 * sum +=  x[srcALen-2] * y[srcBLen-1] + x[srcALen-1] * y[srcBLen-2]
		 * sum +=  x[srcALen-1] * y[srcBLen-1]
		 */

		/* In this stage the MAC operations are decreased by 1 for every iteration.
		   The count variable holds the number of MAC operations performed */
		count = srcBLen - 1u;

		/* Working pointer of inputA */
		pSrc1 = (pIn1 + srcALen) - (srcBLen - 1u);
		px = pSrc1;

		/* Working pointer of inputB */
		pSrc2 = pIn2 + (srcBLen - 1u);
		py = pSrc2;

		/* -------------------
		 * Stage3 process
		 * ------------------*/

		while(blockSize3 > 0) {
			/* Accumulator is made zero for every iteration */
			sum = 0;

			/* Apply loop unrolling and compute 4 MACs simultaneously. */
			k = count >> 2u;

			/* First part of the processing with loop unrolling.  Compute 4 MACs at a time.
			 ** a second loop below computes MACs for the remaining 1 to 3 samples. */
			while(k > 0u) {
				/* sum += x[srcALen - srcBLen + 1] * y[srcBLen - 1] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* sum += x[srcALen - srcBLen + 2] * y[srcBLen - 2] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* sum += x[srcALen - srcBLen + 3] * y[srcBLen - 3] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* sum += x[srcALen - srcBLen + 4] * y[srcBLen - 4] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* Decrement the loop counter */
				k--;
			}

			/* If the count is not a multiple of 4, compute any remaining MACs here.
			 ** No loop unrolling is used. */
			k = count % 0x4u;

			while(k > 0u) {
				/* Perform the multiply-accumulates */
				/* sum +=  x[srcALen-1] * y[srcBLen-1] */
				sum = (q31_t)((((q63_t) sum << 32) +
				               ((q63_t) * px++ * (*py--))) >> 32);

				/* Decrement the loop counter */
				k--;
			}

			/* Store the result in the accumulator in the destination buffer. */
			*pOut++ = sum << 1;

			/* Update the inputA and inputB pointers for next MAC calculation */
			px = ++pSrc1;
			py = pSrc2;

			/* Decrement the MAC count */
			count--;

			/* Decrement the loop counter */
			blockSize3--;

		}

		/* set status as ARM_MATH_SUCCESS */
		status = ARM_MATH_SUCCESS;
	}

	/* Return to application */
	return (status);

}

/**
 * @} end of PartialConv group
 */
